@weirdwriter@dragonscave.space you will need an email provider, like the Gmail you have, or Microsoft Live, or maybe a third party like mail.com (has lots of alias domains).

For cheap email, there are places like mailbox.org. I know they have a temporary email addresses, but not sure which plan.

If you just want to filter spam, places like Gmail, Live, etc support plus (+) addresses, e.g. realemail+alias@gmail.com